MOSTMATHSkill 06 · 7.RP.A.2, 7.RP.A.3

Proportions

A proportion says two ratios are equal. Cross multiply, and the diagonal products match, which turns the proportion into an equation you can solve.

Example · Solve for n.

96=n14\frac{9}{6} = \frac{n}{14}
Steps
  1. Cross multiply. In a true proportion the diagonal products are equal.9⋅14=6⋅n\displaystyle 9 \cdot 14 = 6 \cdot n
  2. That gives 6n = 126. Divide both sides by 6.n=1266=21\displaystyle n = \frac{126}{6} = 21
  3. Check: both fractions reduce to the same thing.96=2114=32\displaystyle \frac{9}{6} = \frac{21}{14} = \frac{3}{2}

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